Everything below concerns peptide fragment. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-09-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
Purity is normally assessed by reversed-phase HPLC, with the main peak reported as a percentage of total peak area, while identity is confirmed by mass spectrometry. Electrospray and MALDI-TOF instruments are both used, and the observed mass is compared with the value calculated from the stated sequence. Ion-exchange or size-exclusion methods appear where aggregation or charge variants are of interest. Water content, counter-ion content and residual trifluoroacetate from purification are separate variables that can shift the measured mass and should be weighed when reading a certificate of analysis.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
| Property | Value | Notes |
|---|---|---|
| Typical form | Lyophilised powder | Reconstituted before use |
| Storage temperature, dry | -20 °C or below | Desiccated, protected from light |
| Purity determination | Reversed-phase HPLC | Reported as percentage of total peak area |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF versus calculated mass |
| Common synonyms | Tβ4 fragment; thymosin beta-4 fragment | Naming varies between suppliers |
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
Thymosin beta-4 itself is a natural peptide of 43 residues found in many cell types and body fluids. Its best-characterised function is binding and sequestering actin monomers, which influences cytoskeletal dynamics. The sequence most often associated with TB-500, LKKTETQ, corresponds to part of that actin-binding region. A different fragment, Ac-SDKP, is also derived from the same parent peptide and is studied in its own right, which is one reason discussions of thymosin fragments can become confusing. The two are structurally distinct and are not interchangeable.
Interest in the fragment grew during the 1990s and 2000s, when it moved from laboratory work into sports and supplement markets. Anti-doping bodies added thymosin beta-4 fragments to prohibited lists, and a small number of adverse analytical findings have been reported in competition testing. Published controlled human trials remain scarce. Most mechanistic evidence comes from cell culture and animal models, and those studies examine endpoints such as cell migration, wound closure and inflammation markers. That evidence supports research interest but does not establish clinical benefit, and broad regenerative claims should be read as unverified.
TB-500 is a short synthetic peptide sold under a trade name rather than a systematic chemical name. Suppliers usually describe it as a fragment of thymosin beta-4 and ship it as a lyophilised powder intended for laboratory use. Because the label is commercial, the exact sequence attributed to it is not fully consistent across catalogues, and some listings present a seven-residue peptide while others describe related fragments of similar length. It is not an approved medicine in any major jurisdiction, and it is handled as a research chemical.
Strontium is named after the Scottish village of Strontian (Scottish Gaelic: Sròn an t-Sìthein), where it was discovered in the ores of the lead mines. In 1790, Adair Crawford, a physician engaged in the preparation of barium, and his colleague William Cruickshank, recognised that the Strontian ores exhibited properties that differed from those in other "heavy spars" sources. This allowed Crawford to conclude on page 355 "... it is probable indeed, that the scotch mineral is a new species of earth which has not hitherto been sufficiently examined." The physician and mineral collector Friedrich Gabriel Sulzer analysed together with Johann Friedrich Blumenbach the mineral from Strontian and named it strontianite. He also came to the conclusion that it was distinct from the witherite and contained a new earth (neue Grunderde). In 1793 Thomas Charles Hope, a professor of chemistry at the University of Glasgow studied the mineral and proposed the name strontites. He confirmed the earlier work of Crawford and recounted: "... Considering it a peculiar earth I thought it necessary to give it an name. I have called it Strontites, from the place it was found; a mode of derivation in my opinion, fully as proper as any quality it may possess, which is the present fashion." The element was eventually isolated by Sir Humphry Davy in 1808 by the electrolysis of a mixture containing strontium chloride and mercuric oxide, and announced by him in a lecture to the Royal Society on 30 June 1808. In keeping with the naming of the other alkaline earths, he changed the name to strontium.
== History == Spontaneous vertebral artery dissection was described in the 1970s. Prior to this, there had been isolated case reports about carotid dissection. In 1971, C. Miller Fisher, a Canadian neurologist and stroke physician working at Massachusetts General Hospital, first noted the "string sign" abnormality in carotid arteries on cerebral angiograms of stroke patients, and subsequently discovered that the same abnormality could occur in the vertebral arteries. He reported the discovery in a paper in 1978.
== Discovery == Islets of Langerhans were first discussed by Paul Langerhans in his medical thesis in 1869. This same year, Édouard Laguesse named them after Langerhans. At first, there was a lot of controversy about what the Islets were made of and what they did. It appeared that all of the cells were the same within the Islet, but were histologically distinct from acini cells. Laguesse discovered that the cells within the Islets of Langerhans contained granules that distinguished them from acini cells. He also determined that these granules were products of the metabolism of the cells in which they were contained. Michael Lane was the one to discover that alpha cells were histologically different than beta cells in 1907. Before the function of alpha cells was discovered, the function of their metabolic product, glucagon, was discovered. The discovery of the function of glucagon coincides with the discovery of the function of insulin. In 1921, Banting and Best were testing pancreatic extracts in dogs that had had their pancreas removed. They discovered that "insulin-induced hypoglycemia was preceded by a transient, rather mild hyperglycemia..." Murlin is credited with the discovery of glucagon because in 1923 they suggested that the early hyperglycemic effect observed by Banting and Best was due to "a contaminant with glucogenic properties that they also proposed to call 'glucagon,' or the mobilizer of glucose". In 1948, Sutherland and de Duve established that alpha cells in the pancreas were the source of glucagon.
Using Mendeleev's nomenclature for unnamed and undiscovered elements, nihonium would be known as eka-thallium. In 1979, IUPAC published recommendations according to which the element was to be called ununtrium (with the corresponding symbol of Uut), a systematic element name as a placeholder, until the discovery of the element is confirmed and a name is decided on. The recommendations were widely used in the chemical community on all levels, from chemistry classrooms to advanced textbooks, but were mostly ignored among scientists in the field, who called it "element 113", with the symbol of E113, (113), or even simply 113. Before the JWP recognition of their priority, the Japanese team had unofficially suggested various names: japonium, after their home country; nishinanium, after Japanese physicist Yoshio Nishina, the "founding father of modern physics research in Japan"; and rikenium, after the institute. After the recognition, the Riken team gathered in February 2016 to decide on a name. Morita expressed his desire for the name to honour the fact that element 113 had been discovered in Japan. Japonium was considered, making the connection to Japan easy to identify for non-Japanese, but it was rejected as Jap is considered an ethnic slur. The name nihonium was chosen after an hour of deliberation: it comes from Nihon (日本), one of the two Japanese pronunciations for the name of Japan.
Invasive garlic mustard, Alliaria petiolata, and its allelochemical benzyl isothiocyanate were shown to inhibit the growth of three species of EcM fungi grown on white pine seedlings. Changes in EcM communities can have drastic effects on nutrient uptake and community composition of native trees, with far-reaching ecological ramifications.
Sources: en.wikipedia.org
== Personal life == Tsien is a 34th-generational descendant of the King of Wuyüeh, Tsien Liu. Tsien's parents Hsue-Chu Tsien and Yi-Ying Li (李懿穎) came from Hangzhou and Beijing, respectively. Tsien had a number of engineers in his extended family, including his father Hsue-Chu Tsien who was an MIT-educated mechanical engineer and his mother's brothers Yao-Tzu Li and Shih-Ying Lee, who were engineering professors at MIT. Tsien's mother Yi-Ying Li was a nurse. The rocket scientist Tsien Hsue-shen, regarded as the cofounding father of the Jet Propulsion Laboratory of the California Institute of Technology and, later, the director of the Chinese ballistic-missile and space programs, is a cousin of Tsien's father. Tsien was the younger brother of Richard Tsien, a neurobiologist at New York University, and Louis Tsien, a software engineer. Tsien, who called his own work molecular engineering, once said, "I'm doomed by heredity to do this kind of work." He was married to Wendy Globe.
Thorium-232 (232Th) is the main naturally occurring isotope of thorium, with a relative abundance of approximately 99.98%. It has a half-life of 14.0 billion years, which makes it the longest-lived isotope of thorium. It decays by alpha decay to radium-228; its decay chain terminates at stable lead-208. Thorium-232 is a fertile material; it can capture a neutron to form thorium-233, which subsequently undergoes two successive beta decays to uranium-233, which is fissile. As such, it has been used in the thorium fuel cycle in nuclear reactors; various prototype thorium-fueled reactors have been designed. However, as of 2024, thorium fuel has not been widely adopted for commercial-scale nuclear power. In 2025, China reported thorium-to-uranium conversion in an experimental molten-salt reactor.
Certain drugs that have been introduced for uses other than analgesics are also used in pain management. Both first-generation (such as amitriptyline) and newer antidepressants (such as duloxetine) are used alongside NSAIDs and opioids for pain involving nerve damage and similar problems. Other agents directly potentiate the effects of analgesics, such as using hydroxyzine, promethazine, carisoprodol, or tripelennamine to increase the pain-killing ability of a given dose of opioid analgesic. Adjuvant analgesics, also called atypical analgesics, include orphenadrine, mexiletine, pregabalin, gabapentin, cyclobenzaprine, hyoscine (scopolamine), and other drugs possessing anticonvulsant, anticholinergic, and/or antispasmodic properties, as well as many other drugs with CNS actions. These drugs are used along with analgesics to modulate and/or modify the action of opioids when used against pain, especially of neuropathic origin. Dextromethorphan has been noted to slow the development of and reverse tolerance to opioids, as well as to exert additional analgesia by acting upon NMDA receptors, as does ketamine. Some analgesics such as methadone and ketobemidone and perhaps piritramide have intrinsic NMDA action. The anticonvulsant carbamazepine is used to treat neuropathic pain. Similarly, the gabapentinoids gabapentin and pregabalin are prescribed for neuropathic pain, and phenibut is available without prescription. Gabapentinoids work as α2δ-subunit blockers of voltage-gated calcium channels, and tend to have other mechanisms of action as well.
== Early life and education == McGuire was born in Fayetteville, Arkansas, and grew up and graduated high school in Mountain Home, Arkansas. He earned a Bachelor of Arts in chemistry, summa cum laude and with Distinction from Hendrix College in Conway, Arkansas. He received his Doctor of Medicine from the Johns Hopkins University School of Medicine, where he was elected to the Alpha Omega Alpha Honor Medical Society. He completed his internship and residency in internal medicine at the University of Texas Southwestern Medical Center, followed by cardiology fellowship training at Duke University School of Medicine. He was a research fellow at the Duke Clinical Research Institute, where he was Chief Fellow from 1999 to 2000, and earned a Master of Health Sciences degree in clinical research.
In January 2001, Lee, Lifeson, and Peart came together to attempt to reassemble the band. According to Peart, "We laid out no parameters, no goals, no limitations, only that we would take a relaxed, civilized approach to the project." With the help of producer Paul Northfield, the band produced seventy-four minutes of music for their new album Vapor Trails, which was written and recorded in Toronto. Vapor Trails marked the first Rush studio recording to not include any keyboards or synthesizers since Caress of Steel. According to the band, the album's developmental process was extremely taxing and took approximately 14 months to finish, the longest they had ever spent writing and recording a studio album. Vapor Trails was released on May 14, 2002; to herald the band's comeback, the single and lead track from the album, "One Little Victory", was designed to grab the attention of listeners with its rapid guitar and drum tempos. The album was supported by the band's first tour in six years, including first-ever concerts in Brazil and Mexico City, where they played to some of the largest crowds of their career. The largest was a capacity crowd of 60,000 in São Paulo. Vapor Trails peaked at No. 3 in Canada and No. 6 in the US, while selling disappointingly in the UK, where it peaked at No. 38.
Sources: en.wikipedia.org
Sealed, desiccated and protected from light, at -20 °C or lower for long-term storage. Short-term storage at refrigerator temperature is common in working laboratories.
Synthesis routes, purification steps and the analytical method used all affect the reported figure. A purity number is only comparable when the chromatographic conditions and detection wavelength are stated.
It reports what the supplier measured on a sample, which is useful but not absolute. Independent mass confirmation on the received lot is the more reliable check.
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.